Portable percussion device



Jan. 8, 1957 Filed Dec. 8, 1951 D. M. PEARSON 2,776,539

PORTABLE PERCUSSION DEVICE 2 Sheets-Sheet-l Fig. 1

'fN Fn/TOIP: FED/V9427 N, FEW/Q60 1957 D. M.'PEARSON 2,776,539

PORTABLE PERCUSSION DEVICE Filed Dec. 8,. 1951 2 Sheets-Sheet 2 Fig. 2

' means nor with stabilizing chambers.

United States Patent 2,776,539 7 PORTABLE PERCUSSION Donald M. Pearson,Oakland, Calif.

Application December 8 1951, Serial No. 260,677

Claims priority, application Germany December 9, 1950 7 Claims. (Cl.60562.5)

Mechanical hammers and chisel apparatus are used in the course of theerection and repairing of various structures. Such apparatusaregenerally referred to as, percussion devices. Such devices have beenequipped with other tools, such as drills. Stationary, transportable andportable percussion devices of this type are well known. The presentinvention is directed to a portable percussion device which may also beused as a traiisportable or a stationary percussion device. I

It is of the greatest importance, that portable percussion devices becompact, handy and light. In spite of these characteristics thesedevices must have a high percussion force, they must be ready foroperation quickly, and it must be possible to adjust in advance thestrength of the percussion force and to manually regulate the latter ina simple manner. Furthermore, the independence of these devices fromstationary driving machines is of considerable importance.

The percussion device according to the invention is provided withelectrical motor means for charging the compressed-air drive and thestrength of the percussion force of the compressed-air piston isincreased by means of -a suction chamber placed in front of the piston.In the embodiment of the invention a one-way valve is disposed in thesuction chamber and an additional chargi'ng device may be provided forthe compressed-air drive.

The portable percussion device constructed according to the inventionrealizes, by means of the above provisions, in a large measure the tasksmentioned above. Particularly favourable working conditions are alsopro-, vided according to the invention because the pressure of thecompressed-air can be regulated, and especially because, between theregulating valve and a hand control equipment, an elastic memberconsisting of a pressure cell is provided, the back of which is loadedby the maxi mum pressure in the cylinder by way of a narrow channel,whereby the narrow channel is connected at its exit with the outer airby means of a valve regulated by a hand control equipment.

In known portable percussion devices charged by means of an electricmotor in order to increase the strength of the percussion force producedby the compressed-air drive, thespace below the compressed-air pistonwas never used to increase thepercussion force.

Therefore, thecompression chamber had to be correspondingly subjected tohigher pressures which, in turn, required the use of a largercompression chamber and of a larger apparatus. Furthermore, heretoforeknown devices were neither provided with pressure regulating; Theoperation of these known devices was, therefore, unsatisfactory andunreliable. On the other hand, applicants portable aparatus isdependable and reliable.

A decisive defect in known percussion devices having. a compressed-aircharge drive affording the percussion force, by means of an electric"motor, resulted from the greatl inferior construction of the geafiiig"mechanism which was disposed between the eleotromotor andthecompressed-air equipment. other characteristics, has corrected thisdefect by 'operating the piston rod of the compressed-air drive througha rotary cam by means of an ele'cttic motor constructed as a unit withthe percussion device.

A specially complete construction according to the invention can beobtainedby the addition of a charging device for the compressed-airdrive. This last men tioned device permits the development in a minimumof time of the pressure needed for operation of the device so that thefull percussion force is reached a few seconds after starting thedevice. Furthermore, the charging device provides a constantcompensation for existing pressure losses and for maintaining thestarting percussion force. This is afforded by the use ofdoublecompressor means whereiii the pressure contributed by at least oneof said compressors can be interrupted; A double-piston system may besubstituted fora doublecompressor.

This doubleiston system includes pistons having uh equal diameters andcan be made integral so as to operable through only one drive or mayinclude a cam portion.

The above objects and other advantages of the invention will becomeapparent from consulting the following detailed description of theinvention when taken in conjunction with the drawings, wherein:

Fig, 1 shows schematically a portable percussion device constructedaccording to the invention;

Fig. la is a sectional view taken along the line III-15d in Fig. l; and

Fig". 2 shows schematically and partly in cross' sectior'r chargingmeans and pressure regulating and controlling means used in conjunctionwith the device of Fig. l.

According to Fig, 1, an electric motor, 4 is located ori a cylinder 2having a bracket portion The electric motor 4 is provided with avertical axle S terminating in a pinion 6, engaging a cog Wheel 7 on ashaft 8.

The shaft 8 is provided with a worm gear 9 which eugages the edges of aworm wheel 9' for driving a boilzontal shaft 10. Shaft 10 is providedwith two opposite cams 11 which are provided with edges shapedapproximately like the development of a logarithmic curve;

A hammer piston 12 provided with conventional packing rings is supportedwithin the cylinder 2 and disp'laceable by'a piston rod 13 which movesthrough a stuffing box 14 and which is provided at one end thereof withan axial bore 17. Rod 16 is fixed on the plate 15 and extends looselyinto bor'e17 of rod 13 so as to guide the latter. Piston rod 13' isfurther provided with a flange 18 which abuts against one of, the edgesof cams If so that upon displacement of cams 11 the piston 12 is movedby the engagement between cams 11 and flange 18.

A small air pump 19' is driven by a cam 20 supported on shaft 8 and iseifective to continuously pump air into compression chamber 22 ofthecylinder 2 through channel 21'.

Compression chamber communicates through marrow channel 23 past needlevalve 25 and openings 26 with the atmosphere Needle valve 25 may beadjusted by displacing handle 24 so that maximum pressure in thecylinder is controlledby the needle valve" 25. A- further regulatingvalve 27 is provided with pressure responsive diaphragm or bellows 28adapted to receive pressure from channel 23. I

A conduit 29 communicates with compresisonchamber 22 and with a pressurestabilizingchamber 3 0 whereby air from the compression chamber 22controls the posi-.

tion of the regulating valve 27 so that said valve opens The invention,apart from under extreme pressure and possibly irregular workingstresses to permit surplus air to escape through outlets 31. A secondcompression chamber 32 communicates by means of passage 33 with thestabilizing chamber so as to further equalize the pressure in chamber 30and to thereby ensure relatively smooth working conditions.

The cylinder 2 is closed at the lower end thereof by a lid 35 withinwhich is arranged a hammer, chisel or drill 36 which is driven by thepiston 12 when same is moved downwardly. Lid 35 is further provided witha valve 37 spring loaded by spring 38 and seated in a cap 39 which isadjustably threaded into lid 35. This one-way valve prevents theformation of a braking air cushion within the suction space 40 ofcylinder 2 and the vacuum existing wtihin space 40 upon upward stroke ofthe piston permits additional acceleration of the motion of the piston12.

Referring more particularly to Fig. 2, the compression chamber 22 of theportable percussion device is very schematically shown, the remainingparts thereof just described being positioned as seen in Fig. 1 abovechamber 22. Charging equipment 41 is connected to compression chamber 22by means of two tubes 42 and 43. Compression chamber 22 is alsoconnected with the valve chamber 45 of a valve 46 through a tube 44.Valve 46 is effective to regulate the percussion force and to decreasethe pressure in compression chamber 22. Obviously, compression chamber22 corresponds to the compression chamber in Fig. l and the hammerpiston 12 and one-way valve 37 extend at the end of compression chamber22 opposite that wherein tube 43 is secured.

The chamber 22 shown in Fig. 2 represents in substance a top plan viewof the cylinder 2 shown in Fig. 1, the latter, of course, having thechamber 22 situated therein at its upper end and above the piston 12.The conduits 42, 43 and 44 communicate with the chamber 22 above thepiston 12 (not shown in Fig. 2), the conduit 42 corresponding to theconduit 21 and the conduit 44 corresponding to the conduit 23 in Fig. 1.The conduit 43 has no counterpart in Fig. l, as the use of this conduitis only suitable for the embodiment of Fig. 2.

A double piston 47 moves in corresponding cylindrical chambers 48 and49, respectively, within charging equipment 41. Double piston 47 isactuated by the cam shaft 50. The cylinder chamber 48 of the pistonhaving the largest diameter is connected through pressure valve 51 andtube 42 with compression chamber 22. This also applies to the cylinderchamber 49 of the piston provided with the smaller diameter since thepressure valve 52 and the tube 43 are connected with cylinder chamber 49and with compression chamber 22. Upon predetermined positioning of thepiston 47 incoming air enters within charging equipment 41 through inletslits 53 or 54 and is compressed by the corresponding portion of piston47. The compressed air is forced into compression chamber 22 throughvalves 51 and 52, respectively. The amount of compressed air forced intosaid compression chamber by cylinder chamber 48 is greater than theamount of compressed air forced into compression chamber 22 bycylindrical chamber 49. Therefore, the portion of the piston 47 havingthe larger diameter charges the compression chamber 22 more rapidly thanthe portion of the piston having the smaller diameter. Actually, theportion of the piston 47 having the smaller diameter merely compensatesany reduction in pressure within compression chamber 22 which resultsfrom leakage.

The pressure generated by the portion of the piston 47 having the largerdiameter can be regulated through slide means 55 and outlet opening 56by hand operated lever 56'. When the pressure in the compression chamber22 is suflicient, further increase in pressure is prevented bypositioning slide 55 so as to permit access by the air under pressure toopening 56. Subsequently, the portion of the piston 47 having a smallerdiameter continues to increase the pressure in the compression chamber22 solely in order to compensate in the manner already described forleakage occurring in compression chamber 22.

The percussion force of the device is controlled by positioning the nut57. According to the position of nut 57 on handle 58, a coil spring 61is compressed by means of bolt 59 engaging with flange sleeve 60. Thiscauses plate 62 to tension valve 64 which is secured to plate 62 by bolt63 and urged against its seat within housing 65. Bolt 63 is axiallybored in order to permit discharge of fluid under pressure from withinvalve chamber 45 to the interior of housing 65.

Conduit 44 interconnects valve chamber 45 and compression chamber 22.Pressure from within compression chamber 22 is transferred through theopening within bolt 63 to one side of plate 62. The force exerted by thespring 61 on the plate 62 is thereby balanced by the pressure existingin compression chamber 22. When the pressure in the compression chamberis increased, the pressure exerted on plate 62 overcomes the strength ofspring 61 and valve '64 is disengaged from its seat in housing 65whereupon, pressure within chamber 22 is decreased and leakage to theatmosphere occurs through outlet opening 67.

Valve chamber 45 is closed at one end by a valve 68 spring loaded bymeans 69. Valve 68 can be adjusted by a bolt 70 by means of a manuallyoperable element or key 71. For instance, the valve 68 can be pushedaway from its seat within housing 65 upon guiding of the end of bolt 70into inclined surface 72 of the key 71. When the operator moves key 71,the force of the percussion force is decreased to a predetermined degreesince the pressure from the compression chamber 22 is released to theatmosphere through tube 44 past valve chamber 45 and outlet conduit 73.Upon release of key 71, the charging equipment 41 again promptlyincreases the pressure within compression chamber 22 up to normaloperating range.

The hammer constructed according to the invention may, obviously, beused for ramming, boring or hammering rivets and the like.

Although one specific embodiment of the invention has been described andshown in the drawings, it should be noted that the invention may berealized in modified form and adaptations of the arrangements hereindisclosed may be made, as may readily occur to persons skilled in theare without constituting a departure from the spirit and scope of theinvention as defined in the objects and in the appended claims.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent, is:

1. In a portable percussion device having piston means displaceable inopposite directions and adapted to force in one of said directions atool element; first means for intermittently pressurizing fluid on oneside of said piston means to thereby displace said piston means in saidone direction, second means operating said first means and operativelyconnected to said piston means to move the latter in opposite directionsand means on the opposite side of said piston means maintaining thereatsaid fluid below atmospheric pressure upon said displacement of saidpiston means in said one direction while preventing charging of saidfluid upon displacement of said piston means in an opposite direction,whereby said pressurized fluid on said one side of said piston meanscooperates with the fluid of less than atmospheric pressure on saidopposite side of said piston means to enhance the effect of said pistonmeans during actuation of said tool element.

2. In a portable percussion device according to claim 1, said secondmeans including driven means, and operable means operatively connectedto said driven means to thereby displace said piston means in saidopposite direction.

3. In a portable percussion device according to claim 2, wherein saidoperable means is in the form of rotatable cam means, a portion of saidcam means being engageable With a portion extending from said pistonmeans for moving the latter in said opposite direction.

4. In a portable percussion device according to claim 1, including meansfor regulating the maximum pressure of said fluid on said one side ofsaid piston means.

5. In a portable percussion device according to claim 4, said regulatingmeans including means responsive to predetermined fluid pressureprevailing on said one side of said piston means for permittingdischarge of said pressurized fluid.

6. A percussion device having a cylinder, a piston with a piston rodarranged for movement in said cylinder in opposite directions, and motordrive means for driving said piston in one of said directions;comprising, driven means operatively connected with said motor drivemeans and including means operatively connecting said driven means withsaid piston rod to thereby move said piston in one direction, fluidcompression means intermittently actuated by said driven means andconnected to said cylinder, whereby fluid under pressure from said fluidcompression means is admitted to said piston for moving the latter in anopposite direction and against an element to be actuated, and meanslocated in said cylinder maintaining a fluid pressure below atmosphericpressure therein, when said piston is moved in said one direction.

7. In a portable percussion device having piston means for actuating atool element and adapted to be displaced by fluid under pressure actingon the high pressure side of said piston means; means for pressurizingsaid fluid and including reciprocating fluid pump means acting on saidhigh pressure side of said piston means, drive means for actuating saidpump means and provided with cam means for reciprocating said pump meansand said piston means simultaneously, pressure regulating valve meansfor controlling the maximum pressure of said fluid, and valve means onthe low pressure side of said piston means for permitting the dischargeof fluid located at the loW pressure side of said piston means andthereby assisting the actuation of said tool element by said pistonmeans.

References Cited in the file of this patent UNITED STATES PATENTS399,789 Scott Mar. 19, 1889 847,945 Ilett Mar. 19, 1907 1,024,395 CantyApr. 23, 1912 1,874,752 Hirsch Aug. 30, 1932 2,306,600 George Dec. 29,1942

